Magnetic resonance (MR) is known to allow quantitative measurements of molecular diffusion in different materials (e.g., diffusion of water molecules in biological tissues, diffusion of gas in the lung). Such materials are frequently composed of structural units (e.g., structural units such as cells in biological tissues, airways in lungs, pores in rocks). Boundaries of these units serve as restrictive barriers for diffusing molecules. In case of structurally (geometrically) anisotropic units, molecular diffusion is also anisotropic and can be described by a tensor of diffusion coefficients. If structural units are of sufficient size to be resolved by direct imaging, the tensor of diffusion coefficients can be determined for each structural unit by means of MR imaging with multiply-oriented diffusion-sensitizing gradients.
There is a need for a method and system which allows extracting information on diffusion tensor components in cases where the anisotropic structural units are too small to be resolved by direct imaging and a multitude of differently oriented structural anisotropic units is present in a single imaging voxel. In cases when orientation of these units is random, there is also a need for a method and system in which only diffusion-sensitizing magnetic field gradients oriented in one direction are needed for data acquisition and analysis to extract information on diffusion tensor components.
The invention described below addresses one or more of these and other disadvantages and needs.